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Posted 30 July 2015. PMN Crop News.

Soybean Double Cropping After Small Grain Harvest- When is too Late?

Source: Penn State University Press Release.

University Park, Pennsylvania (July 14, 2015)--This year has changed the game when it comes to double cropping soybeans. Typically as July progresses after small grain harvest producers no till soybeans. The late timing this year might be an issue for other recrop forages after small grains, however with continued rains and ideal planting conditions many producers will continue to plant. I have seen fields planted directly after barley that did emerge almost immediately with the rains. We have ample moisture in the soil right now and it appears that some is in the forecast.


It takes about 90 days for soybeans to develop pods and dry seed so if we get an average frost we need to be planting beans by July 15- August 1 in Pa to be in the window for harvest based on average frost free dates. The Pa Average First Frost date map indicates that some areas frost about November 1 in Pa so those areas could still plant soybeans. Here are some other considerations.

1. Plan to establish at least a 180,000 ppa so to achieve that a minimum planted population of 200,000 is recommended for double crop beans prior to July 5 after which 220,000 ppa might be in order to ensure ideal canopy cover.

2. Plant narrow row less than 15 and 7 inch or narrower preferred. There is less time for the soybeans to gain height to pod so the narrow rows allows for more beans to grow at higher populations.

3. If the field has visible weeds be sure to burn down to ensure weed competition is kept to a minimum.

4. Set a realistic economic target. Traditional double crop yields of 30bu/acre is not out of the question (we typically see about a 50% response the first week of July)and at $9/bushel soybeans there is some but not a lot of room to spend input costs over and above that which needs to be spent to make the crop. This simple table best illustrates the impact of planting date.

5. Be aware that the potential for a early frost is possible and if forage is needed consider management for a forage use of the soybean. If the goal is forage supply then perhaps sorghum sudan or other annual crop may be a better selection.

6. Maturity considerations. There has been talk about moving to a shorter maturity. Past experience in this area would suggest full season maturities for double crops may out yield short season maturities. Our double crop beans planted with full maturity over the last several years have matured with no ill problems in the fall. Last season which was also a wet season our Lancaster Double Crop Soybean Trials averaged 54bu/acre planted on June 24th at 220,000ppa. To view the maturity and varieties please visit Pennsylvania Soybean Performance Test 2014. Dr. Dave Holshour from Virginia Tech related the impact of maturity on delayed planting. For April and May plantings, a 3 day delay in planting resulted in a 1 day delay in maturity. For example, planting 30 days late would cause a 10 day maturity delay. However in the June and July plantings, a 5 day delay in planting resulted in only a 1 day difference in maturity. Most important is to plant a maturity group that would grow as long as possible in the vegetative stage to gain height before flowering which allows for an adequate canopy for maximum yield and still mature before a frost.

Finally Dr. Greg Roth and I are looking at other parameters for double crop soybeans that might prove useful in the future to further add yield to this late plant timing. We are revisiting row width, date of planting, growth regulators, seed treatments and other practices to ensure recommendations stay current. Stay tuned for more information as the Mid Atlantic begins to focus on this double crop timing.

Delbert Voight